PaperRater.com is a free resource, developed and maintained by linguistics professionals and graduate students. PaperRater.com is used by schools and universities in over 46 countries to help students improve their writing.
PaperRater.com combines the power of natural language processing (NLP), artificial intelligence (AI), machine learning, information retrieval (IR), computational linguistics, data mining, and advanced pattern matching (APM). We offer the most powerful writing tool available on the internet today.
UPDATE: Be cautious when uploading documents for them as according to the Terms and Conditions you give them the right to use your documents.